The present invention generally relates to a supercharger control in an automobile engine system and, more particularly, to a control system for controlling an engine-driven, supercharging pump used in association with an automobile engine.
When it comes to the supercharged automobile engine system, two types are generally well known in the art depending on the type of supercharger; one using the turbosupercharger or, simply, turbocharger, driven by the flow of exhaust gases, and the other using a compressor or air pump driven by either an engine or an electric motor. The present invention pertains to the use of the air pump as a source of supercharged air to be supplied to the engine.
A supercharged automobile engine system using an engine-driven air pump, so far considered pertinent to the present invention, is disclosed in, for example, Japanese Laid-open Patent Publication Nos. 58-30414 and 58-30415, both published Feb. 22, 1983. In publication No. 58-30414, an air intake passage extending from an air cleaner to an engine cylinder has an engine-driven, vane-type air pump and a throttle valve installed on upstream and downstream sides, respectively, with respect to the direction of flow of air towards the engine cylinder, and a bypass passage bypassing only the air pump and a control valve installed therein for selective opening and closure of the bypass passage. The air pump used therein is drivingly coupled with the engine through an electromagnetic clutch for selectively coupling and decoupling the air pump with and from the engine, respectively. Both the throttle valve and the control valve are operatively coupled with an accelerator pedal through a mechanical linkage system and are controlled in an opposite sense to each other.
Publication No. 58-30414 makes use of an electromechanical supercharger control connected physically with a link system between the accelerator pedal and the control valve on the one hand, and electrically with the electromagnetic clutch on the other hand. The supercharger control disclosed therein is so designed and so operable that, when the throttle valve being moved from a substantially closed position towards a fully open position as a result of the displacement of the accelerator pedal from a released position towards a fully depressed position attains a first predetermined opening, he clutch can be energized, and kept energized, to couple the air pump with the engine to effect the supply of the supercharged air, but when the throttle valve once having attained the first predetermined opening attains a second predetermined opening smaller than the first predetermined value as a result of the displacement of the accelerator pedal back towards the released position, the clutch can be deenergized to decouple the air pump from the engine to interrupt the supply of the supercharged air.
On the other hand, the control valve in the bypass passage normally held in a fully open position when the throttle valve is in the substantially closed position can be brought to a completely closed position for interrupting the flow of air through the bypass passage, but directing it towards the air pump, subsequent to the start of operation of the air pump, i.e., when and after the throttle valve being moved towards the fully open position has exceeded a third predetermined opening greater than any one of the first and second predetermined values.
The supercharger control is shown and described as including a rotatably supported disc plate having different peripheral portions operatively coupled respectively with the accelerator pedal and the control valve, and two self-energizing circuits operatively associated with each other, one of said self-energizing circuits including two series-connected switches adapted to be successively actuated by a common actuator pin carried by the disc plate.
As acknowledged in publication No. 58-30415, the system of publication No. 58-30414, although effective to operate the air pump to provide the supercharged air when the automobile is desired to be accelerated from a moderate or high speed drive, has a problem in that it cannot be accelerated as desired immediately after the start of the automobile and from a low speed drive because under these circumstances the accelerator pedal is not, and has not yet been, depressed enough to cause the throttle opening to exceed the first predetermined value. More specifically, even though a condition is established wherein a rapid acceleration is desired to be achieved (i.e., wherein the degree of requirement for acceleration is great and the air pump is desired to be operated to quickly increase the engine output torque while the engine is operating under a low load range), the air pump cannot be operated before a high load range is established particularly where the load on the engine at which the air pump starts its operation is set at a relatively high value. Alternatively, where the load on the engine at which the air pump starts its operation is set at a relatively low value, even though a condition is established wherein a moderate acceleration is desired to be achieved (i.e., wherein the degree of requirement for acceleration is small and the air pump is desired to be operated while the engine is operated under a relatively high load range), the air pump tends to be operated, while the engine is operating under a low load range, resulting in the unduly rapid acceleration.
In view of the foregoing, publication No. 58-30415 discloses an improved version which may be considered a combination with the supercharge control of publication No. 58-30414 of another supercharge control operable only when a gear shift lever is in any one of first and second gear positions in view of the fact that acceleration is particularly required when the automobile transmission is set in a low speed range such as first or second gear position. In other words, publication No. 58-30415 assumes that at the start of the automobile the transmission is usually set in the first or second gear position, and starting from this assumption, the use of such another supercharger control has been made together with a microswitch capable of generating an energizing signal to the electromagnetic clutch in response to the setting of the transmission in the low speed range. In one form of the control of publication No. 58-30415, the use is made of an additional control valve disposed in the bypass passage and adapted to be controlled by an electromagnetic actuator energizeable in response to, or a predetermined delay time (necessitated to avoid any possible surging of the air pump) after, the generation of the energizing signal to interrupt the flow of air through the bypass passage. However, in another form of the same control, the control valve of publication No. 58-30414 is utilized also for interrupting the flow of air through the bypass passage during the setting of the transmission in the low speed range, and for this purpose, a unique mechanical linkage is used to connect the control valve with the accelerator pedal on the one hand and with the electromagnetic actuator on the other hand.
Under those circumstances which have been discussed in both of these publications, the supercharger control is so designed according to the second mentioned publication No. 58-30415 as to operate the air pump not only during the setting of the transmission in the low speed range, but also during the moderate or high speed operating condition of the engine appears to be satisfactory. However, in view of the fat that, once the transmission has been set in the low speed range, the supply of the supercharged air takes place regardless of the operating condition then assumed by the engine, some problems have been found. For example, the air pump tends to be operated to eventually increase the engine power output even during a low speed, low load operating condition, which often occurs during a low speed cruising (that is, where the degree of requirement for acceleration is small), and therefore, the engine power output cannot be adequately adjusted without any difficulty. Moreover, during the descent of the automobile down the slope with the transmission set in the first gear position, it may happen that the engine braking will not work and the automobile will run wayward beyond the driver's control.